Benign prostatic hyperplasia (BPH) is a common medical condition in men. The current standard treatment for BPH is transurethral resection of the prostate (TURP). More than 400,000 men in the United States undergo TURP each year. The requirements of general anesthesia and hospitalization for TURP add to the relatively high morbidity and cost of this procedure, fueling the search for less invasive and less costly alternatives. Ablation by microwave energy of the hyperplastic prostatic tissues causing urethral constriction is one such alternative to TURP. Transurethral microwave thermotherapy (TUMT) preserves the integrity of the urethra, reduces morbidity, and can be done without general anesthesia and hospitalization. The success of TUMT is largely dependent on achieving intraprostatic temperatures of 60 - 70 degrees C for about one hour, but no methods are currently available to monitor intraprostatic temperatures noninvasively during treatment. This proposal is intended to develop a noninvasive method of monitoring both urethral and intraprostatic temperature during TUMT through the use of passive microwave radiometry (PMR). PMR has several advantages over existing fiberoptic thermal sensing systems. Although both can measure temperature in a microwave field and not perturb the homogeneity of the field, PMR is less costly, more durable and noninvasive. This technique would permit urologists to accumulate thermal information in a noninvasive way during TUMT which would be more predictive of treatment outcome. PROPOSED COMMERCIAL APPLICATIONS: A reliable noninvasive method of monitoring both urethral and intraprostatic temperature during microwave ablation of BPH has obvious potential for manufacturers of commercially-available microwave ablation systems currently using thermal monitoring methods which are more costly, perturbing to the microwave field, fragile or invasive.